摘要 |
PURPOSE:To cover the decrease in the characteristics of a permanent magnet by providing an auxiliary coil in a magnetic circuit of a linear DC motor and varying a current flowing through the coil in response to the temperature rise. CONSTITUTION:Permanent magnets 3A, 3B are provided at both ends of yokes 1A, 1B, auxiliary coils 4A, 4B are respectively wound on the magnets 3A, 3B, and a thermistor 5 is mounted in the vicinity of the magnet 3A. Magnetic circuits 6A, 6B which have circuits from the magnets 3A, 3B, through the yoke 1A, a gap G and a yoke 1B to the magnets 3A, 3B are ordinary formed, and a thrust is produced by the action of the magnetic circuits and the current flowing through a movable coil 2. When the temperature of a linear DC motor increases, the resistance of the thermistor 5 will vary, and the currents flowing through the coils 4A, 4B will increase. In this manner, the magnetic fluxes generated in the magnetic circuits 6A, 6B can be maintained constantly even if the temperature varies. |